Okay, assuming for now that the dock is hooked up correctly, let's look at the way that you have the video conversion set up. You mentioned that the receiver is connected to the TV using HDMI. Therefore, you'll need to have the receiver set up to convert the analog video from the iPod and output it through the HDMI output.
Page 19 of the receiver's
owner's manual shows a diagram of the video conversion flow. Starting on page 98, the manual describes the settings for allowing the analog video input to be output through HDMI. Stepping through them:
1. Turn video conversion to "On".
2. Set the HDMI resolution setting appropriately (on page 99)
Give that a try, if you haven't already, and let us know if it works. Thanks!